The Doc's tranny waggin' Options

[Dr Evil]

So, the head was mailed today to the Corvair Ranch for valve seat exam/repair and final assembly. I was tired of messing with it. I will finish the CC of it when it gets home and assemble (IMG:style_emoticons/default/smile.gif)

[scotty b]

(IMG:style_emoticons/default/dry.gif) butcher (IMG:style_emoticons/default/dry.gif)

[rick 918-S]

Hey doc, Two words. Family Practice. Your skills as a surgeon worry me. (IMG:style_emoticons/default/happy11.gif)

[Dr Evil]

Blah blah.

When I did the other head I left the old valves in to protect the seats....I thought I was more skilled and didnt need to do that with this head (IMG:style_emoticons/default/dry.gif) ah well, its only $$ (IMG:style_emoticons/default/sad.gif)

[Dr Evil]

Let us pontificate on the future of a CIS system on this mill. In my research I have found at least one other individual that had attempted, futilely, to put both a Corvair engine and CIS into his bus. This resulted in no improvement, crappy running and decreased, abysmal fuel mileage.

[Dr Evil]

Why do you think this set up didnt work?

[rick 918-S]

Hard to say from those photos but where is the fuel distributor? Biggest issue with CIS as I see it is fuel pressure and learning how to set it at the WUR. It took me years (really) to figure out why mine was all over the map. Vaccum is also an issue.

REfresh me on what parts you are using for your CIS. 911 stuff?

I never worked on CIS before my Alien build. There are three guys in town that have CIS experience. Two of them are the exclusive Volvo guys. The other guy is a Volvo, Ferrari and VW guy. I couldn't even pay these guys with an open check book to help me or take the car in to tune it. If I can help you I will. CIS is easy once you get the fuel pressure set.

PS: don't bother messing with the adjustment at the fuel distributor. It is for fine tuning only not for fuel pressure. Every CIS guy here in town came out to the car with a long allen wrench and dicked with the dizzy adjustment only to foul it up more than it was when I brought it to them.

[Dr Evil]

All of the parts except the housing as I will make my own. Making my own down tubes, too. I will be using the Volvo distributor housing.

[rick 918-S]

All of the parts except the housing as I will make my own. Making my own down tubes, too. I will be using the Volvo distributor housing.

Are you using 4 intake runners or 6? How are you using a Volvo Dizzy if it's 6 runners? Bertone V6 engine stuff?

[Dr Evil]

My system consists of:
Stock 3.0 CIS from 911
Distributor mount/air box from Volvo - remote mount
Heads are as in the pic, individual ports
Aftermarket fuel pump with appropriate pressure and flow rating

Thanks for the call, Rick. I have considered that the guy whose engine is pictured above did not know exactly what he was doing.

My intentions are to make a plenum that is closer to the fan, and shorter down tubes. I am not sure where the injectors are going, yet, but this guy may have them too far away from the valve which would cause a rich running condition.

Things that I considered with this guys report, if all pressures and plumbing were correct:
- Injector location
- Plenum and down tube volume (his look large). Too large and response is slow, too small and response is erratic.
- System used. I am not sure what he got his CIS out of.

[Dr Evil]

Some more ramblings about the engine:

Stock CR for a corvair 140 is 9.25:1

I was running 7.25:1 and it was kicking ass, but running rough. Now I am manning up and raising the CR to stock or there about.

Bore 94mm
Stroke 74.6125mm
Head gasket .04in
Deck height .038in (I need to verify. I cant find my notes, and my calc has .08 in the collumn (IMG:style_emoticons/default/dry.gif) )
Chamber 50cc
Pistons are flat top

In my research I have found that the magic # for higher CR and no detonation is a clearance of about .04" between quench and the piston top.

[scotty b]

Problem #1 :

he used a 924/audi t.b. that was designed for a 2.0 liter 4 cylinder

Problem # 2 :

The runners a REALLY long for a 3.0+ engine thus creating more top end h.p. than low end that a bus really needs

Problem # 3 :

The T.B. is effectivey at a 180* bend to the runners thus creating an extremely awkward flow into an already lenghty runner

Problem # 4:

In my experiecne most people DO NOT know hw CIS works and DO NOT know how to set it up and " tune it "

[rick 918-S]

Sheeze! That's what me and Doc were talking about today. (IMG:style_emoticons/default/laugh.gif) That plemium is too small and the throttle body is in a very weird place. The 928 is directly under a very large plenium aith a direct connection to the fuel dizzy.

[strawman]

Hey Doc --

One other thing to consider with CIS is the fuel lines. I shoehorned a Golf Mk2 1.8 engine into a factory diesel Vanagon Westfalia many years ago. I was warned that the fuel lines MUST be made using very high quality SS-jacketed material to stabilize the CIS "pulses." Apparently, cheapo lines that bulge can wreak havoc on the system. I can't remember what company I paid (dearly!) to make those longer-than-stock lines, but I never had any problems with the setup. YMMV.

Geoff

[Dr Evil]

Problem #1 :

he used a 924/audi t.b. that was designed for a 2.0 liter 4 cylinder

Problem # 2 :

The runners a REALLY long for a 3.0+ engine thus creating more top end h.p. than low end that a bus really needs

Problem # 3 :

The T.B. is effectivey at a 180* bend to the runners thus creating an extremely awkward flow into an already lenghty runner

Problem # 4:

In my experiecne most people DO NOT know hw CIS works and DO NOT know how to set it up and " tune it "

Good eye, Scott. I would not have know that about the TB. Mine will likely be better. With you and Rick, we all agree that most dont know how to tune the CIS. That book you lent me helped me understand a lot so that this should be a no brainer. (IMG:style_emoticons/default/smile.gif)

[Dr Evil]

Every time you let a project linger, you loose things (IMG:style_emoticons/default/dry.gif) I did some work today on the engine, sort of. I made a fixture to hold the barrels in place today so I can work on the other side while I await the return of my other head.



I got the other 3 pistons cleaned up and then I could not find the damn clips for the rod pins (IMG:style_emoticons/default/dry.gif) Looks like I will have to source some more (IMG:style_emoticons/default/headbang.gif)

[Dr Evil]

Happy day!

I found my clips for the pistons so I installed the P/C. I checked the new deck height and it is 0.063". I rechecked a chamber on the head and it was 50cc. I installed the head and began working the rocker geometry out (IMG:style_emoticons/default/smile.gif)

[Dr Evil]

After very little trial and error, the pattern was perfect and the rod length locked in (IMG:style_emoticons/default/smile.gif) Now I need to wait for the other head to come back, and to send these rods off to be measured and matched. They are longer than stock by a bit.

[Dr Evil]

So, for those of you keeping score at home, here are the stats:

Bore = 94mm
Stroke = 74.6125mm
Deck = 0.063"
Chamber volume = 50cc

I am leaving the head gaskets off as they drop the CR lower than I want (<9). With no head gasket the Cr = 9.47:1 (IMG:style_emoticons/default/smilie_pokal.gif)

[rick 918-S]

The CIS will like the compression. BTW: do you have an accumulator? You need to use an accumulator. That's what reduces the pulse in the fuel system. I used one from a Volvo turbo CIS car.